Add Supported class to dart:html

tools/dom/src/dart2js_Platform.dart

Index: tools/dom/src/dart2js_Platform.dart
diff --git a/tests/language/issue9602_other.dart b/tools/dom/src/dart2js_Platform.dart
similarity index 67%
copy from tests/language/issue9602_other.dart
copy to tools/dom/src/dart2js_Platform.dart
index a189b7759b4381e2a8a27289c2b7ca318915f85a..90570f004991ddb2e87080fe4ac66e4b525b72be 100644
--- a/tests/language/issue9602_other.dart
+++ b/tools/dom/src/dart2js_Platform.dart
@@ -2,9 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// Regression test case for http://dartbug.com/9602
-library issue9602_other;
+part of html;
 
-class M {
-  var _field;
+class Platform {
+  static final supportsTypedData = JS('bool', '!!(window.ArrayBuffer)');
 }